As a fuel cell, there is conventionally known a solid oxide fuel cell (hereinafter sometimes abbreviated as “SOFC”) using a solid electrolyte (solid oxide).
One known use of SOFC is as a fuel cell stack, which has stacked therein a plurality of fuel cells, each including a plate-shaped solid electrolyte layer (solid oxide layer), a fuel electrode layer disposed on one side of the solid electrolyte layer and an air electrode layer disposed on the other side of the solid electrolyte layer.
The SOFC is so configured as to generate electrical power by supplying fuel gas and air to the fuel electrode layer and the air electrode layer, respectively, and causing chemical reaction of the fuel and oxygen in the air through the solid electrolyte layer.
It has been proposed to provide the SOFC with a serial fuel gas flow structure for improvement of fuel utilization rate (see Patent Document 1). The serial fuel gas flow structure allows a flow of the fuel gas to some fuel cells in parallel with a flow of the fuel gas discharged from these some fuel cells to the other fuel cells in the fuel cell stack.
Further, there has recently been proposed a technique in which a plurality of manifolds are formed through the fuel cell stack in a stacking direction thereof such that the fuel gas and air are supplied to or discharged from the respective fuel cells through the manifolds (see Patent Documents 2 and 3).